1. Technical Field
The inventive concept described herein relates to a semiconductor memory, and more particularly relates to a memory system that uses a DRAM as a cache and a cache management method thereof.
2. Discussion of Related Art
A semiconductor memory may refer to a memory device that is implemented using a semiconductor such as silicon (Si), germanium (Ge), gallium arsenide (GaAs), or indium phosphide (InP). A semiconductor memory device may be classified as a volatile memory device or a nonvolatile memory device. A volatile memory device is a type of storage device whose contents are erased when the system's power is turned off or interrupted. A nonvolatile memory device is a type of memory that can retrieve stored information even after having been power cycled.
A flash memory is widely used as the nonvolatile memory device since it has a large capacity, is quiet, and uses little power. In particular, a flash memory-based solid state drive (SSD) is used as mass storage in a personal computer, a notebook, a workstation, a server system, and the like. In addition, the SSD may be used as a nonvolatile mass storage that is over-writable and nonvolatile.
A storage system may use a dynamic random access memory (DRAM) as a cache memory and a nonvolatile memory as a storage device. However, various issues may occur because the DRAM communicates data in a different manner from the nonvolatile memory.